The present invention relates to disc drives. More specifically, the present invention relates to determining a data fill-in frequency used to write to a disc in a disc drive during servo writing.
Disc drives illustratively include data transducers located relative to disc surfaces of rotatable discs in a disc stack. The data transducers are provided with a write signal to encode data on the disc surface. When the disc surface is moved relative to the data transducer, the data transducer generates a read signal indicative of data which has already been encoded on the disc.
In order to write data to the disc, a servo system is used to position the data head at one of a plurality of concentric tracks on the disc surface. A disc drive controller then provides information which generates the write signal that is provided to the data transducer. The data transducer thus encodes data on the disc surface at the desired track location.
When a read operation is to be performed, the servo system again positions the data transducer relative to a desired track on the disc surface. The data transducer then generates a read signal indicative of information encoded on the track over which the data transducer is positioned. This information is provided back to the drive controller which identifies data based on the read signal received.
It can thus be seen that, in order to perform a read or write, the servo system must perform a track following operation. In a track following operation, the servo system holds the data transducer over a track on the disc surface, while the disc rotates, to read data from, or write data to, the disc surface. In order to access a desired portion of the disc surface, the servo system must perform a track seek operation. In the track seek operation, the servo system moves the data transducer radially relative to the disc surface to a desired one of the concentric tracks to be accessed.
The data is stored in concentric tracks on each disc surface. The tracks are separated into various fields including a synchronization field, a field containing header information, a data field, etc. The concentric tracks on a given disc surface are separated from one another by a track-to-track guardband. In order to ensure correct track seeking or searching during the drive power-up process, a pattern with a predetermined frequency is written into the track-to-track guardband. Then, when a drive is powered up, the servo firmware first looks for the servo sectoring direct current (DC) field for synchronization and decodes the consecutive servo Gray code samples. However, if the track-to-track guardband is filled with, for example, a DC erase pattern, this pattern will misguide the data head to an incorrect track.
In some prior art disc drives, the guardbands on the media surfaces have been filled with a 40 MHz servo pattern. The guardband writing process is normally known as pack-writing. The data field is filled with a multi-frequency pattern. A certain degree of the guardband servo pattern frequency couples to the reader, causing some impact on the read back signal-to-noise ratio (SNR) in the data field. This causes the bit error rate (BER) at some zones to degrade by more than a decade.
The present invention addresses one or more of these deficiencies.
A guardband portion is written on a disc surface in a disc drive. A predetermined data pattern is written on at least one data track adjacent to the guardband portion. A predetermined guardband pattern is written at a plurality of different guardband frequencies in the guardband portion. For each guardband frequency, at least one performance criterion is measured for the data track. A desired guardband pattern is written on the guardband portion of the disc surface at a guardband frequency chosen based on the measured performance criterion.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.